A return to large-scale features of Pliocene climate: the Pliocene Model Intercomparison Project Phase 2

Abstract. The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental consequences of an atmospheric CO2 concentration near ~ 400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resolution and based on new reconstructions of boundary conditions (the Pliocene Model Intercomparison Project Phase 2; PlioMIP2). As a global annual average, modelled surface air temperatures increase by between 1.4 and 4.7 °C relative to pre-industrial with a multi-model mean value of 2.8 °C. Annual mean total precipitation rates increase by 6 % (range: 2 %–13 %). On average, surface air temperature (SAT) increases are 1.3 °C greater over the land than over the oceans, and there is a clear pattern of polar amplification with warming polewards of 60° N and 60° S exceeding the global mean warming by a factor of 2.4. In the Atlantic and Pacific Oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. Although there are some modelling constraints, there is a statistically significant relationship between a model's climate response associated with a doubling in CO2 (Equilibrium Climate Sensitivity; ECS) and its simulated Pliocene surface temperature response. The mean ensemble earth system response to doubling of CO2 (including ice sheet feedbacks) is approximately 50 % greater than ECS, consistent with results from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea-surface temperatures are used to assess model estimates of ECS and indicate a range in ECS from 2.5 to 4.3 °C. This result is in general accord with the range in ECS presented by previous IPCC Assessment Reports.

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The Pliocene Model Intercomparison Project Phase 2: large-scale climate features and climate sensitivity

Climate of the Past ◽

10.5194/cp-16-2095-2020 ◽

2020 ◽

Vol 16 (6) ◽

pp. 2095-2123 ◽

Cited By ~ 4

Author(s):

Alan M. Haywood ◽

Julia C. Tindall ◽

Harry J. Dowsett ◽

Aisling M. Dolan ◽

Kevin M. Foley ◽

...

Keyword(s):

Climate Sensitivity ◽

Large Scale ◽

Climate Models ◽

Temperature Response ◽

Surface Air Temperature ◽

System Response ◽

Phase 2 ◽

Model Intercomparison ◽

Intergovernmental Panel ◽

Intercomparison Project

Abstract. The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental consequences of an atmospheric CO2 concentration near ∼400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resolution based on new reconstructions of boundary conditions (the Pliocene Model Intercomparison Project Phase 2; PlioMIP2). As a global annual average, modelled surface air temperatures increase by between 1.7 and 5.2 ∘C relative to the pre-industrial era with a multi-model mean value of 3.2 ∘C. Annual mean total precipitation rates increase by 7 % (range: 2 %–13 %). On average, surface air temperature (SAT) increases by 4.3 ∘C over land and 2.8 ∘C over the oceans. There is a clear pattern of polar amplification with warming polewards of 60∘ N and 60∘ S exceeding the global mean warming by a factor of 2.3. In the Atlantic and Pacific oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. There is a statistically significant relationship between a model's climate response associated with a doubling in CO2 (equilibrium climate sensitivity; ECS) and its simulated Pliocene surface temperature response. The mean ensemble Earth system response to a doubling of CO2 (including ice sheet feedbacks) is 67 % greater than ECS; this is larger than the increase of 47 % obtained from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea surface temperatures are used to assess model estimates of ECS and give an ECS range of 2.6–4.8 ∘C. This result is in general accord with the ECS range presented by previous Intergovernmental Panel on Climate Change (IPCC) Assessment Reports.

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Reduced complexity model intercomparison project phase 1: Protocol, results and initial observations

10.5194/gmd-2019-375 ◽

2020 ◽

Cited By ~ 1

Author(s):

Zebedee R. J. Nicholls ◽

Malte Meinshausen ◽

Jared Lewis ◽

Robert Gieseke ◽

Dietmar Dommenget ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Models ◽

Phase 1 ◽

Coupled Model ◽

Surface Air Temperature ◽

Internal Variability ◽

Second Phase ◽

Model Intercomparison ◽

Intercomparison Project ◽

Reduced Complexity

Abstract. Here we present results from the first phase of the Reduced Complexity Model Intercomparison Project (RCMIP). RCMIP is a systematic examination of reduced complexity climate models (RCMs), which are used to complement and extend the insights from more complex Earth System Models (ESMs), in particular those participating in the Sixth Coupled Model Intercomparison Project (CMIP6). In Phase 1 of RCMIP, with 14 participating models namely ACC2, AR5IR (2 and 3 box versions), CICERO-SCM, ESCIMO, FaIR, GIR, GREB, Hector, Held et al. two layer model, MAGICC, MCE, OSCAR and WASP, we highlight the structural differences across various RCMs and show that RCMs are capable of reproducing global-mean surface air temperature (GSAT) changes of ESMs and historical observations. We find that some RCMs are capable of emulating the GSAT response of CMIP6 models to within a root-mean square error of 0.2 °C (of the same order of magnitude as ESM internal variability) over a range of scenarios. Running the same model configurations for both RCP and SSP scenarios, we see that the SSPs exhibit higher effective radiative forcing throughout the second half of the 21st Century. Comparing our results to the difference between CMIP5 and CMIP6 output, we find that the change in scenario explains approximately 46 % of the increase in higher end projected warming between CMIP5 and CMIP6. This suggests that changes in ESMs from CMIP5 to CMIP6 explain the rest of the increase, hence the higher climate sensitivities of available CMIP6 models may not be having as large an impact on GSAT projections as first anticipated. A second phase of RCMIP will complement RCMIP Phase 1 by exploring probabilistic results and emulation in more depth to provide results available for the IPCC's Sixth Assessment Report author teams.

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Comparing different generations of idealized solar geoengineering simulations in the Geoengineering Model Intercomparison Project (GeoMIP)

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-4231-2021 ◽

2021 ◽

Vol 21 (6) ◽

pp. 4231-4247

Author(s):

Ben Kravitz ◽

Douglas G. MacMartin ◽

Daniele Visioni ◽

Olivier Boucher ◽

Jason N. S. Cole ◽

...

Keyword(s):

Climate Models ◽

Net Primary Productivity ◽

Hydrological Cycle ◽

Co2 Concentration ◽

Global Scale ◽

Model Intercomparison ◽

Two Generations ◽

Temporary Solution ◽

Solar Geoengineering ◽

Intercomparison Project

Abstract. Solar geoengineering has been receiving increased attention in recent years as a potential temporary solution to offset global warming. One method of approximating global-scale solar geoengineering in climate models is via solar reduction experiments. Two generations of models in the Geoengineering Model Intercomparison Project (GeoMIP) have now simulated offsetting a quadrupling of the CO2 concentration with solar reduction. This simulation is idealized and designed to elicit large responses in the models. Here, we show that energetics, temperature, and hydrological cycle changes in this experiment are statistically indistinguishable between the two ensembles. Of the variables analyzed here, the only major differences involve highly parameterized and uncertain processes, such as cloud forcing or terrestrial net primary productivity. We conclude that despite numerous structural differences and uncertainties in models over the past two generations of models, including an increase in climate sensitivity in the latest generation of models, the models are consistent in their aggregate climate response to global solar dimming.

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Stratocumulus Clouds in Southeastern Pacific Simulated by Eight CMIP5–CFMIP Global Climate Models

Journal of Climate ◽

10.1175/jcli-d-13-00376.1 ◽

2014 ◽

Vol 27 (8) ◽

pp. 3000-3022 ◽

Cited By ~ 25

Author(s):

Jia-Lin Lin ◽

Taotao Qian ◽

Toshiaki Shinoda

Keyword(s):

Cloud Cover ◽

Large Scale ◽

Climate Models ◽

Global Climate ◽

Cloud Feedback ◽

Global Climate Models ◽

Temperature Structure ◽

Model Intercomparison ◽

Stratocumulus Clouds ◽

Intercomparison Project

Abstract This study examines the stratocumulus clouds and associated cloud feedback in the southeast Pacific (SEP) simulated by eight global climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) and Cloud Feedback Model Intercomparison Project (CFMIP) using long-term observations of clouds, radiative fluxes, cloud radiative forcing (CRF), sea surface temperature (SST), and large-scale atmosphere environment. The results show that the state-of-the-art global climate models still have significant difficulty in simulating the SEP stratocumulus clouds and associated cloud feedback. Comparing with observations, the models tend to simulate significantly less cloud cover, higher cloud top, and a variety of unrealistic cloud albedo. The insufficient cloud cover leads to overly weak shortwave CRF and net CRF. Only two of the eight models capture the observed positive cloud feedback at subannual to decadal time scales. The cloud and radiation biases in the models are associated with 1) model biases in large-scale temperature structure including the lack of temperature inversion, insufficient lower troposphere stability (LTS), and insufficient reduction of LTS with local SST warming, and 2) improper model physics, especially insufficient increase of low cloud cover associated with larger LTS. The two models that arguably do best at simulating the stratocumulus clouds and associated cloud feedback are the only ones using cloud-top radiative cooling to drive boundary layer turbulence.

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On the Correspondence between Mean Forecast Errors and Climate Errors in CMIP5 Models

Journal of Climate ◽

10.1175/jcli-d-13-00474.1 ◽

2014 ◽

Vol 27 (4) ◽

pp. 1781-1798 ◽

Cited By ~ 78

Author(s):

H.-Y. Ma ◽

S. Xie ◽

S. A. Klein ◽

K. D. Williams ◽

J. S. Boyle ◽

...

Keyword(s):

Large Scale ◽

Climate Models ◽

Systematic Errors ◽

Cmip5 Models ◽

Model Intercomparison ◽

Short Term ◽

Climate Simulations ◽

Intercomparison Project ◽

Short And Long Term

Abstract The present study examines the correspondence between short- and long-term systematic errors in five atmospheric models by comparing the 16 five-day hindcast ensembles from the Transpose Atmospheric Model Intercomparison Project II (Transpose-AMIP II) for July–August 2009 (short term) to the climate simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and AMIP for the June–August mean conditions of the years of 1979–2008 (long term). Because the short-term hindcasts were conducted with identical climate models used in the CMIP5/AMIP simulations, one can diagnose over what time scale systematic errors in these climate simulations develop, thus yielding insights into their origin through a seamless modeling approach. The analysis suggests that most systematic errors of precipitation, clouds, and radiation processes in the long-term climate runs are present by day 5 in ensemble average hindcasts in all models. Errors typically saturate after few days of hindcasts with amplitudes comparable to the climate errors, and the impacts of initial conditions on the simulated ensemble mean errors are relatively small. This robust bias correspondence suggests that these systematic errors across different models likely are initiated by model parameterizations since the atmospheric large-scale states remain close to observations in the first 2–3 days. However, biases associated with model physics can have impacts on the large-scale states by day 5, such as zonal winds, 2-m temperature, and sea level pressure, and the analysis further indicates a good correspondence between short- and long-term biases for these large-scale states. Therefore, improving individual model parameterizations in the hindcast mode could lead to the improvement of most climate models in simulating their climate mean state and potentially their future projections.

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Eddy-resolving Simulation of CAS-LICOM3 for Phase 2 of the Ocean Model Intercomparison Project

Advances in Atmospheric Sciences ◽

10.1007/s00376-020-0057-z ◽

2020 ◽

Vol 37 (10) ◽

pp. 1067-1080

Author(s):

Yiwen Li ◽

Hailong Liu ◽

Mengrong Ding ◽

Pengfei Lin ◽

Zipeng Yu ◽

...

Keyword(s):

Large Scale ◽

Ocean Model ◽

Meridional Overturning Circulation ◽

Western Boundary ◽

Preliminary Evaluation ◽

Phase 2 ◽

Model Intercomparison ◽

Sst Variability ◽

Intercomparison Project ◽

Resolution Simulation

Abstract A 61-year (1958–2018) global eddy-resolving dataset for phase 2 of the Ocean Model Intercomparison Project has been produced by the version 3 of Chinese Academy of Science, the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics (LASG/IAP) Climate system Ocean Model (CAS-LICOM3). The monthly and a part of the surface daily data in this study can be accessed on the Earth System Grid Federation (ESGF) node. Besides the details of the model and experiments, the evolutions and spatial patterns of large-scale and mesoscale features are also presented. The mesoscale features are reproduced well in the high-resolution simulation, as the mesoscale activities can contribute up to 50% of the total SST variability in eddy-rich regions. Also, the large-scale circulations are remarkably improved compared with the low-resolution simulation, such as the climatological annual mean SST (the RMSE is reduced from 0.59°C to 0.47°C, globally) and the evolution of Atlantic Meridional Overturning Circulation. The preliminary evaluation also indicates that there are systematic biases in the salinity, the separation location of the western boundary currents, and the magnitude of eddy kinetic energy. All these biases are worthy of further investigation.

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Comparing different generations of idealized solar geoengineering simulations in the Geoengineering Model Intercomparison Project (GeoMIP)

10.5194/acp-2020-732 ◽

2020 ◽

Cited By ~ 1

Author(s):

Ben Kravitz ◽

Douglas G. MacMartin ◽

Daniele Visioni ◽

Olivier Boucher ◽

Jason N. S. Cole ◽

...

Keyword(s):

Climate Models ◽

Net Primary Productivity ◽

Hydrological Cycle ◽

Co2 Concentration ◽

Global Scale ◽

Model Intercomparison ◽

Cloud Forcing ◽

Temporary Solution ◽

Solar Geoengineering ◽

Intercomparison Project

Abstract. Solar geoengineering has been receiving increased attention in recent years as a potential temporary solution to offset global warming. One method of approximating global-scale solar geoengineering in climate models is via solar reduction experiments. Two generations of models in the Geoengineering Model Intercomparison Project (GeoMIP) have now simulated offsetting a quadrupling of the CO2 concentration with solar reduction. This simulation is artificial and designed to elicit large responses in the models. Here we show that energetics, temperature, and hydrological cycle changes in this experiment are statistically indistinguishable between the two ensembles. Of the variables analyzed here, the only major differences involve highly parameterized and uncertain processes, such as cloud forcing or terrestrial net primary productivity. We conclude that despite numerous structural differences and uncertainties in models over the past 20 years, including an increase in climate sensitivity in the latest generation of models, broad conclusions about the climate response to global solar dimming remain robust.

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Large-scale features and evaluation of the PMIP4-CMIP6 <i>midHolocene</i> simulations

Climate of the Past ◽

10.5194/cp-16-1847-2020 ◽

2020 ◽

Vol 16 (5) ◽

pp. 1847-1872 ◽

Cited By ~ 7

Author(s):

Chris M. Brierley ◽

Anni Zhao ◽

Sandy P. Harrison ◽

Pascale Braconnot ◽

Charles J. R. Williams ◽

...

Keyword(s):

Large Scale ◽

Climate Models ◽

Hydrological Cycle ◽

Global Climate ◽

Coupled Model ◽

Global Climate Models ◽

Current Phase ◽

Model Intercomparison ◽

Global Mean Temperature ◽

Intercomparison Project

Abstract. The mid-Holocene (6000 years ago) is a standard time period for the evaluation of the simulated response of global climate models using palaeoclimate reconstructions. The latest mid-Holocene simulations are a palaeoclimate entry card for the Palaeoclimate Model Intercomparison Project (PMIP4) component of the current phase of the Coupled Model Intercomparison Project (CMIP6) – hereafter referred to as PMIP4-CMIP6. Here we provide an initial analysis and evaluation of the results of the experiment for the mid-Holocene. We show that state-of-the-art models produce climate changes that are broadly consistent with theory and observations, including increased summer warming of the Northern Hemisphere and associated shifts in tropical rainfall. Many features of the PMIP4-CMIP6 simulations were present in the previous generation (PMIP3-CMIP5) of simulations. The PMIP4-CMIP6 ensemble for the mid-Holocene has a global mean temperature change of −0.3 K, which is −0.2 K cooler than the PMIP3-CMIP5 simulations predominantly as a result of the prescription of realistic greenhouse gas concentrations in PMIP4-CMIP6. Biases in the magnitude and the sign of regional responses identified in PMIP3-CMIP5, such as the amplification of the northern African monsoon, precipitation changes over Europe, and simulated aridity in mid-Eurasia, are still present in the PMIP4-CMIP6 simulations. Despite these issues, PMIP4-CMIP6 and the mid-Holocene provide an opportunity both for quantitative evaluation and derivation of emergent constraints on the hydrological cycle, feedback strength, and potentially climate sensitivity.

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Evaluating the large-scale hydrological cycle response within the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble

Climate of the Past ◽

10.5194/cp-17-2537-2021 ◽

2021 ◽

Vol 17 (6) ◽

pp. 2537-2558

Author(s):

Zixuan Han ◽

Qiong Zhang ◽

Qiang Li ◽

Ran Feng ◽

Alan M. Haywood ◽

...

Keyword(s):

Indian Ocean ◽

Large Scale ◽

Hydrological Cycle ◽

Hadley Circulation ◽

Dynamic Effect ◽

Phase 2 ◽

Model Intercomparison ◽

Northern Indian Ocean ◽

Thermodynamic Effect ◽

Intercomparison Project

Abstract. The mid-Pliocene (∼3 Ma) is one of the most recent warm periods with high CO2 concentrations in the atmosphere and resulting high temperatures, and it is often cited as an analog for near-term future climate change. Here, we apply a moisture budget analysis to investigate the response of the large-scale hydrological cycle at low latitudes within a 13-model ensemble from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The results show that increased atmospheric moisture content within the mid-Pliocene ensemble (due to the thermodynamic effect) results in wetter conditions over the deep tropics, i.e., the Pacific intertropical convergence zone (ITCZ) and the Maritime Continent, and drier conditions over the subtropics. Note that the dynamic effect plays a more important role than the thermodynamic effect in regional precipitation minus evaporation (PmE) changes (i.e., northward ITCZ shift and wetter northern Indian Ocean). The thermodynamic effect is offset to some extent by a dynamic effect involving a northward shift of the Hadley circulation that dries the deep tropics and moistens the subtropics in the Northern Hemisphere (i.e., the subtropical Pacific). From the perspective of Earth's energy budget, the enhanced southward cross-equatorial atmospheric transport (0.22 PW), induced by the hemispheric asymmetries of the atmospheric energy, favors an approximately 1∘ northward shift of the ITCZ. The shift of the ITCZ reorganizes atmospheric circulation, favoring a northward shift of the Hadley circulation. In addition, the Walker circulation consistently shifts westward within PlioMIP2 models, leading to wetter conditions over the northern Indian Ocean. The PlioMIP2 ensemble highlights that an imbalance of interhemispheric atmospheric energy during the mid-Pliocene could have led to changes in the dynamic effect, offsetting the thermodynamic effect and, hence, altering mid-Pliocene hydroclimate.

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Projected Changes in Late-Twenty-First-Century Tropical Cyclone Frequency in 13 Coupled Climate Models from Phase 5 of the Coupled Model Intercomparison Project

Journal of Climate ◽

10.1175/jcli-d-13-00010.1 ◽

2013 ◽

Vol 26 (24) ◽

pp. 9946-9959 ◽

Cited By ~ 58

Author(s):

K. J. Tory ◽

S. S. Chand ◽

J. L. McBride ◽

H. Ye ◽

R. A. Dare

Keyword(s):

Tropical Cyclone ◽

Large Scale ◽

Climate Models ◽

Coupled Model ◽

Reanalysis Data ◽

First Century ◽

Model Intercomparison ◽

Intercomparison Project ◽

Twenty First Century ◽

Projected Changes

Abstract Changes in tropical cyclone (TC) frequency under anthropogenic climate change are examined for 13 global models from phase 5 of the Coupled Model Intercomparison Project (CMIP5), using the Okubo–Weiss–Zeta parameter (OWZP) TC-detection method developed by the authors in earlier papers. The method detects large-scale conditions within which TCs form. It was developed and tuned in atmospheric reanalysis data and then applied without change to the climate models to ensure model and detector independence. Changes in TC frequency are determined by comparing TC detections in the CMIP5 historical runs (1970–2000) with high emission scenario (representative concentration pathway 8.5) future runs (2070–2100). A number of the models project increases in frequency of higher-latitude tropical cyclones in the late twenty-first century. Inspection reveals that these high-latitude systems were subtropical in origin and are thus eliminated from the analysis using an objective classification technique. TC detections in 8 of the 13 models reproduce observed TC formation numbers and geographic distributions reasonably well, with annual numbers within ±50% of observations. TC detections in the remaining five models are particularly low in number (10%–28% of observed). The eight models with a reasonable TC climatology all project decreases in global TC frequency varying between 7% and 28%. Large intermodel and interbasin variations in magnitude and sign are present, with the greatest variations in the Northern Hemisphere basins. These results are consistent with results from earlier-generation climate models and thus confirm the robustness of coupled model projections of globally reduced TC frequency.

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